1. FREE DRIVINGThe driver proceeds at his or her desired speed pro-vided there are no obstacles in front of him or her. Such obstacles may include, for example, slow moving vehicles, red traffic lights or potential collisions with vehicles changing lanes.

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2. APPROACHINGThe driver recognises that there is a slow moving vehicle in front of him or her and brakes within the desired gap. In PTV Vissim, it is possible to define different driver and vehicle characteristics for different vehicle classes and types, such as the rate of decele-ration when approaching the vehicle in front.

3. FOLLOWINGThe driver tries to maintain his or her distance from the vehicle in front when fol-lowing it. However, the distance between the two vehicles oscillates – some-times the speed is slightly higher, sometimes lower.

4. BRAKINGIf a vehicle reduces its speed downstream, then the vehicle behind must also brake. For each vehicle, Vissim checks in each simulation time step the distance and the differences in speed in relation to the vehicle in front.

SIMULATING DRIVING BEHAVIOUR

The modelling of driving behaviour is the core of trafficsimulation. Vehicle movement models are a key element in being able to replay dynamics in a realistic manner. A distinction is made between three models:

The psycho-physical car-following model by Prof. Rainer Wiedemann was developed at the Karlsruhe Institute of Technology in 1974 and 1999. It describes the movement of traffic on a single lane. The model is implemented in the PTV Vissim simulation software and can be adjusted by the user via parameters in line with local conditions.

The vehicle following model describes 4 states:

FOLLOWING MODEL

LANE CHANGING There are two different types of lane changing:

NON-LANE BASED BEHAVIOURThe choice of position within a lane is always important if vehicles are able to overtake each other within a particular lane and are able to be side-by-side. This is the case on cycle paths or on regular streets in certain regions, for example.

1. FREE LANE CHANGINGFree lane changing takes place when over- taking slow moving vehicles, i.e. when an individual’s desired speed is higher than the person in front. Attention must be paid to ensure that vehicles in the other lane are not unduly affected by this.

2. NECESSARY LANE CHANGINGThis occurs if the driver needs to change lane, e.g. in order to follow a route. The closer the driver gets to the decision-making point, the more aggressively the driver behaves and is prepared to accept the hindrances posed by other drivers. Other vehicles also co-operate in order to allow the driver to change lanes.

ONLY INPTV Vissim

LATERAL BEHAVIOUR WITHIN A LANE